The physical space of the MSK Library is scheduled to close to visitors on Friday, May 17, 2024. Please visit this guide for more information.
The physical space of the MSK Library is scheduled to close to visitors on Friday, May 17, 2024. Please visit this guide for more information.
Highly pathogenic avian influenza (HPAI) A(H5) viruses have been detected in U.S. wild aquatic birds, commercial poultry and backyard or hobbyist flocks beginning in January 2022. These are the first detections of HPAI A(H5) viruses in the U.S. since 2016. Preliminary genetic sequencing and RT-PCR testing on some virus specimens shows these viruses are HPAI A(H5N1) viruses from clade 2.3.4.4.
NOTE: On March 29, 2024 the CDC announced new interim recommendations for prevention, monitoring, and public health investigations of highly pathogenic avian influenza A(H5N1) virus in animals. Updates to this page are forthcoming.
| Dairy Cattle: On-going multi-state outbreak | Humans: 2 cases in the U.S. |
| Wild Birds: Widespread | Person-to-person spread: None |
| Poultry Flocks: Sporadic outbreaks | Current public health risk: Low |
| Mammals: Sporadic infections |
USDA’s Food Safety and Inspection Service (FSIS) is announcing results from its testing of retail ground beef. FSIS collected 30 samples of ground beef from retail outlets in the states with dairy cattle herds that had tested positive for the H5N1 influenza virus at the time of sample collection. The samples were sent to APHIS’ National Veterinary Services Laboratories (NVSL) for PCR testing. On May 1, NVSL reported that all samples tested negative for H5N1. These results reaffirm that the meat supply is safe.
Dr. Barb Petersen, a dairy veterinarian in Amarillo, Texas, had been caring for sick cows for several weeks in March when she and a colleague finally pinned down the cause of the illness among the herd: the H5N1 strain of the bird flu.
During that same time, she said, dairy workers — including those who were never in close contact with the sick cows — also fell ill.
“People had some classic flu-like symptoms, including high fever, sweating at night, chills, lower back pain,” as well as upset stomach, vomiting and diarrhea, Petersen said. “They also tended to have “pretty severe conjunctivitis and swelling of their eyelids.”
Petersen noted that the people were never tested for H5N1; it’s possible that their symptoms were the result of another illness.
So far just one person, a dairy worker in Texas, has tested positive for the virus. The person’s case was mild, the Centers for Disease Control and Prevention said. The only symptom involved was conjunctivitis, or pinkeye.
At least 44 others may have been exposed, the CDC said. Some have been tested, while others were asked to monitor symptoms, such as cough, sore throat, pinkeye, fever, headache and diarrhea.
Dr. Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory, said he’s heard reports of flu-like illnesses on affected dairy farms. “It’s certainly not a large amount,” he said, “but there’s probably a lot of cases that are not documented.”
Today, the FDA received some initial results from its nationally representative commercial milk sampling study. The agency continues to analyze this information; however, the initial results show about 1 in 5 of the retail samples tested are quantitative polymerase chain reaction (qPCR)-positive for HPAI viral fragments, with a greater proportion of positive results coming from milk in areas with infected herds.
As previously noted and outlined in our summary below, qPCR-positive results do not necessarily represent actual virus that may be a risk to consumers. Additional testing is required to determine whether intact pathogen is still present and if it remains infectious, which would help inform a determination of whether there is any risk of illness associated with consuming the product.
The FDA has received additional results from an initial limited set of geographically targeted samples as part of its national commercial milk sampling study underway in coordination with USDA. The FDA continues to analyze this information; however, preliminary results of egg inoculation tests on quantitative polymerase chain reaction (qPCR)-positive retail milk samples show that pasteurization is effective in inactivating HPAI.
This additional testing did not detect any live, infectious virus. These results reaffirm our assessment that the commercial milk supply is safe.
In addition, several samples of retail powdered infant formula were tested, as well as powdered milk products marketed as toddler formula. All qPCR results of formula testing were negative, indicating no detection of viral fragments or virus in powdered formula products.
The FDA is further assessing retail samples from its study of 297 samples of retail dairy products from 38 states. All samples with a PCR positive result are going through egg inoculation tests, a gold-standard for determining if infectious virus is present.
Epidemiological signals from our CDC partners continue to show no uptick of human cases of flu and no cases of H5N1, specifically, beyond the one known case related to direct contact with infected cattle.
While CDC believes the current risk to the general public remains low, people with close or long unprotected exposures (not wearing respiratory or eye protection) to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals, are at greater risk of infection.
Clinicians should consider the possibility of HPAI A(H5N1) virus infection in people showing signs or symptoms of acute respiratory illness or conjunctivitis and who have relevant exposure history outlined in Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations.
Starting empiric antiviral treatment with oral or enterically administered oseltamivir (twice daily for five days) is recommended regardless of time since onset of symptoms. Antiviral treatment should not be delayed while waiting for laboratory test results.
The United States has the strongest avian influenza surveillance program in the world. Through our ongoing wild bird surveillance program, APHIS collects and tests large numbers of samples from wild birds in the North American flyways.
It is not uncommon to detect avian influenza in wild birds, as avian influenza viruses circulate freely in those populations without the birds appearing sick. In addition to monitoring for avian influenza in wild bird populations, APHIS monitors for the virus in commercial and backyard birds.
With the recent detections of the Eurasian H5 strain of highly pathogenic avian influenza (HPAI) in wild birds and domestic poultry in the United States, bird owners should review their biosecurity practices and stay vigilant to protect poultry and pet birds from this disease. APHIS is working closely with State partners on surveillance, reporting, and control efforts.
APHIS confirmed highly pathogenic avian influenza (HPAI) in a commercial flock in the United States on February 8, 2022. Since then, we have worked swiftly to identify and respond to detections and mitigate the virus’ impact on U.S. poultry production and trade. Detections are higher in the fall and spring, because we continue to see wild birds spreading virus as they migrate to their seasonal homes. APHIS continues to work closely with State animal health officials on surveillance efforts to look for the virus in commercial, backyard, and wild birds.
Wild birds can be infected with highly pathogenic avian influenza (HPAI) and show no signs of illness. They can carry the disease to new areas when migrating, potentially exposing domestic poultry to the virus.
APHIS’ wild bird surveillance program provides an early warning system for the introduction and distribution of avian influenza viruses of concern in the United States, allowing APHIS and the poultry industry to take timely and rapid action to reduce the risk of spread to our poultry industry and other populations of concern.
There are many species that are potentially susceptible to highly pathogenic avian influenza (HPAI). In addition to birds and poultry, H5N1 viruses have been detected in some mammals (see list below). Infection may cause illness, including severe disease and death in some cases.
The U.S. Department of Agriculture, Food and Drug Administration, Centers for Disease Control and Prevention, and State veterinary and public health officials are investigating an illness among primarily older dairy cows.
